From 1802 to 1921, Eleutherian Mills was a gunpowder mill site used for the manufacture of explosives by the Du Pont family business. The name also refers to the house on the hill above the mills, which was the first Du Pont family home in America. The business was founded by Eleuthère Irénée du Pont. In 1952, the site became an outdoor museum and the Hagley Museum and Library was founded.[3]

They set up the Eleutherian gunpowder mill on the Brandywine Creek just north of Wilmington, Delaware, based on gunpowder machinery bought from France and site plans for a gunpowder mill supplied by the French Government.[6] They also built housing for 30 workers.[4]

Starting, initially, by reworking damaged gunpowder and refining saltpetre for the US Government they quickly moved into gunpowder manufacture.[6]

Saltpetre was refined in an area between the house and the mills that now is occupied by a formal garden. Charcoal was produced from the willow trees that lined the Brandywine.

By the end of 1804, DuPont had sold 39,000 pounds of powder; the following year sales tripled. The Federal government and John Jacob Astor's American Fur Company became regular customers. In 1813 the Hagley property, just downstream from the original mills, was purchased, doubling the size and capacity of the mills. Sales grew during the Mexican-American War and the Crimean War. During the American Civil War, the firm sold 4,000,000 barrels of powder to the Federal government.

A major explosion killed 33 people in 1818. Another major explosion occurred on the site in 1847. In 1854 three gunpowder wagons exploded in the city of Wilmington.

Mill race which supplied water power to the mills. A railway car is on the right

The mill buildings used in the manufacture of gunpowder were built with strong stone-walled structures on three sides; but were only covered by light wood structures on the fourth side, which faced out onto the Brandywine Creek. When an accident occurred, the explosion was directed away from the other mills and storage areas and over the creek.

Water power was provided from a mill race behind the mills, thus further isolating the mills in case of accident. One water wheel was often used to provide power to two mills. Water turbines were introduced in the 1840s. Alfred Victor du Pont acquired additional property, down stream from the Eleutherian Mills, to add to the manufacturing site. One of these properties was called Hagley, and it became known as the Hagley Yard.

Unrestored mill on the Brandywine

Edge-runner mill in a restored mill

Most of the industrial remains are located in the Hagley Yard. The mills were used in the purification, crushing, and mixing of charcoal, sulfur, and saltpeter. Other mills in the complex were used for glazing and corning, making metal powder kegs, and in cotton and woolen manufacturing. Stables, offices, a machine shop, and a steam powerhouse from the late 19th century also were located in the complex, as was a narrow gauge railway.